U.S. patent number 6,535,262 [Application Number 10/078,145] was granted by the patent office on 2003-03-18 for display unit for chip cards with folded sheet a method for manufacturing such a display unit.
This patent grant is currently assigned to Infineon Technologies AG. Invention is credited to Detlef Houdeau.
United States Patent |
6,535,262 |
Houdeau |
March 18, 2003 |
Display unit for chip cards with folded sheet a method for
manufacturing such a display unit
Abstract
A display unit includes activation or driver electronics
disposed on the rear side of a display element. A display unit has
a front region with a display element; a rear region, facing away
from the front region, with at least one control element for the
activation of the at least one display element; and electrical
lines for the connection of the at least one display element to the
at least one control element. Preferably, an LCD display with a top
layer, a liquid crystal layer, and a bottom sheet is used. The
control element is disposed on the bottom sheet. The control
element is, for example, an unpackaged IC, that is attached to the
bottom sheet folded back on itself and is laterally offset in such
a way that it cannot overheat the actual LCD display. The
electrical lines are preferably conductor tracks on the bottom
sheet.
Inventors: |
Houdeau; Detlef (Langquaid,
DE) |
Assignee: |
Infineon Technologies AG
(Munich, DE)
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Family
ID: |
7918759 |
Appl.
No.: |
10/078,145 |
Filed: |
February 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCTDE0002812 |
Aug 18, 2000 |
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Foreign Application Priority Data
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Aug 18, 1999 [DE] |
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199 39 106 |
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Current U.S.
Class: |
349/150; 349/151;
349/160 |
Current CPC
Class: |
G02F
1/13452 (20130101) |
Current International
Class: |
G02F
1/13 (20060101); G02F 001/133 () |
Field of
Search: |
;349/151,160,150 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 350 176 |
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Apr 1974 |
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DE |
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24 27 335 |
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Jan 1975 |
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DE |
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31 05 981 |
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Nov 1981 |
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DE |
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196 04 374 |
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Aug 1997 |
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DE |
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0 831 420 |
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Mar 1998 |
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EP |
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0 940 771 |
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Sep 1999 |
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EP |
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WO 99/31646 |
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Jun 1999 |
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WO |
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Other References
Minowa, T. et al.: "A New Construction Approach to Liquid Crystal
Display Instrument for Automobiles", Warrendale, 1982, pp.
47-50..
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Primary Examiner: Ton; Toan
Assistant Examiner: Schechter; Andrew
Attorney, Agent or Firm: Greenberg; Laurence A. Stemer;
Werner H. Locher; Ralph E.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of copending International
Application No. PCT/DE00/02812, filed Aug. 18, 2000, which
designated the United States.
Claims
I claim:
1. A display unit for chip cards, the display unit having a front
side and a rear side, comprising; a display element having a top
sheet, a bottom sheet, and a liquid crystal layer provided as a
display for the front side of the display unit; a control element
being electrically connected to said display element through said
bottom sheet and disposed on the rear side of the display unit; and
said bottom sheet including: an upper side, said display element
and said control element being fastened to said upper side; and a
fold being located between said display element and said control
element and defining two opposing faces of said upper side, one of
said opposing faces facing toward said liquid crystal layers the
other of said opposing faces facing away from said liquid crystal
layer; said control element being disposed laterally from said
display element and on said face facing away from said liquid
crystal layer.
2. The display unit according to claim 1, including: an edge on
said bottom sheet; and electrical lines leading around said edge of
said bottom sheet.
3. The display unit according to claim 1, wherein said control
element is an integrated circuit without a package.
4. A method of producing an LCD display element for chip cards,
which comprises: providing a display element having a liquid
crystal layer; providing a control element; providing a bottom
sheet with a side having conductor tracks and a region extending
beyond the liquid crystal layer; attaching the display element on
the side of the bottom sheet; attaching the control element on the
side of the bottom sheet in the region extending beyond the liquid
crystal layer; folding the bottom sheet between the display element
and the control element to form on the bottom sheet an edge, a face
facing toward the liquid crystal layer, and a face facing away from
the liquid crystal layer holding the control element, which is
disposed laterally from said display element; and leading the
conductor tracks around the edge of the bottom sheet.
Description
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a display unit in which the activation or
driver electronics are disposed on the rear side of a display
element.
Flat displays based on LED or LCD technology are increasingly being
used in the area of data processing equipment or communication and
entertainment electronics. In the process, LCD (liquid crystal
diode) technologies are especially becoming widely accepted, on the
basis of their contrast, low necessary current and favorable
production costs. A customary LCD display in this case includes a
top plate that covers the actual liquid crystal element with the
liquid crystals and a bottom plate on which the liquid crystal
element with the actual liquid crystals is mounted. This sandwich
method achieves good protection for the sensitive liquid
crystals.
For the electrical activation of the individual liquid crystals,
the bottom plate is made larger than the actual liquid crystal, to
allow contacts for leading away signal lines to be attached to it.
It is customary to use what is known as a flex circuit, that is to
say a flat ribbon cable with numerous individual signal lines, to
allow the signals to be led to the bottom plate. The actual
activation or driver electronics is/are consequently separate from
the display unit.
It has also been proposed to dispose the control electronics
directly on the protruding part of the bottom plate or bottom glass
sheet. Both configurations, known in the prior art, have the
disadvantage, however, that the bottom plate must be significantly
larger than the actual display area, to allow the flat ribbon cable
or the activation electronics to be fastened on it.
Integration of displays, such as LCD displays, in what are known as
chip cards has so far not been possible at all on account of the
confined lateral space, but in particular on account of the small
thickness of chip cards of only at most 0.84 mm (according to ISO
7816, 10373). However, on account of the growing significance of
chip cards and the increasing functionality accommodated on them,
it would be advantageous also to provide a display capability on
chip cards. This applies in particular when a capability of
recharging with data or a monetary value is to be used for the
purpose of repeated usability.
In the case of customary displays, moreover, the separation of the
actual display area and the control electronics involves additional
expenditure and further possible sources of faults. It would
therefore be advantageous to have a display unit that is more
compact, involves lower expenditure to produce and assemble and
could possibly be included in chip cards.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a display
unit and a method for manufacturing a display unit that overcome
the hereinafore-mentioned disadvantages of the heretofore-known
devices and methods of this general type.
With the foregoing and other objects in view, there is provided, in
accordance with the invention, a display unit for chip cards. The
display unit includes a display element having a front side, a rear
side, and a liquid crystal layer for the front side of the display
unit. The display unit also includes a control element being
electrically connected to the display element and disposed as an
integrated circuit on the rear side of the display unit opposite
from the front side.
With the objects of the invention in view, there is also provided a
method of producing an LCD display element for chip cards. The
first step of the method is providing a display element having a
liquid crystal layer. The next step is providing a control element.
The next step is providing a bottom sheet with a side having
conductor tracks and a region extending beyond the liquid crystal
layer. The next step is attaching the display element on the side
of the bottom sheet. The next step is attaching the control element
on the side of the bottom sheet in the region extending beyond the
liquid crystal layer. The next step is folding the bottom sheet
between the display element and the control element to form an edge
on the bottom sheet, a face facing toward the liquid crystal layer,
and a face facing away from the liquid crystal layer that holds the
control element. The next step is leading the conductor tracks
around the edge of the bottom sheet.
In one aspect, the invention is directed at a display unit in which
a control element is positioned directly behind a display
element.
In a further aspect, the invention is directed at a display unit of
which the base area corresponds substantially to the base area of
the liquid crystal.
In another aspect, the invention is directed at a display unit in
which it has been possible for fault-prone plug-in connections
largely to be minimized.
Accordingly, the invention is directed at a display unit with a
front region with at least one display element, a rear region
facing away from the front region, with at least one control
element for the activation of the at least one display element and
electrical lines for the connection of the at least one display
element to the at least one control element.
A control element is to be understood here as meaning any
electronic device that is capable of making the respectively used
display elements display informational contents. For example, the
control element may have a driver circuit or a number of circuits
that convert the signals coming from an information-representing
device into electric currents suitable for the display element.
The control element may in this case be disposed directly on the
rear region or be encapsulated by a package. The package improves
the control element stability with respect to external influences.
A display element for the purposes of the present invention is
understood here as meaning any substantially flat element that is
suitable for the display of information, for example multi-element
LED display modules, multi-element LCD display modules, which are
suitable for the representation of numeric or alphanumeric
information, matrix-based LED, LCD or plasma screens, mechanically
displaying elements, etc. In this case, one or a number of the
display elements respectively used may actually be used, for
example a number of LED modules, which are respectively suitable
for the display of a figure or a letter.
It is particularly preferred for the display element to have an LCD
display. A display element that includes different types of
individual elements is also conceivable.
When an LCD display is used, it is preferred for it to have a top
layer, a liquid crystal layer, a bottom sheet, and for at least one
control element to be disposed on the bottom sheet. The
configuration of the control element on the bottom sheet may take
place by techniques familiar to a person skilled in the art, for
example by adhesive attachment, solder, fixing by common frame,
etc. The top layer may, in the way already customary in the case of
today's LCD displays, include glass. It may, however, also include
a plastic sheet to reduce the thickness of the LCD display and
increase the mechanical flexibility, as is necessary for example
for use in chip cards. To avoid the absorption of moisture, the
plastic sheet may be additionally provided with at least one
water-vapor barrier layer.
Also, when other display elements are used as an LCD display, it is
preferred for the control element to be disposed directly on the
rear side of the at least one display element. In this case, the
display element also may have a bottom sheet or bottom plate, which
forms its rear side, it then being possible for the control element
to be fastened to the bottom sheet or to the bottom plate.
The control element may have a package with a socket. The socket
may be connected directly to the bottom sheet or bottom plate. In
the case of driver circuits, which have a higher power demand, and
as a result greater heat dissipation, this configuration improves
cooling. Moreover, it is possible to comply exactly with
specifications with respect to the desired depth of a display unit
by using socket adapters. When included in chip cards, a socket
would increase the thickness of the unit, possibly making it
impossible for it to be included. Socketed packages are therefore
not preferred when the display units according to the invention are
used in chip cards.
The use of packages and sockets is prevented when the displays
according to the invention are used in chip cards, because the
latter are too thin to be able to accommodate control elements with
packages. Therefore, it is preferred as an alternative for the
control element to be an integrated circuit without a package,
which is connected directly to the bottom sheet or bottom plate.
The mounting of the integrated circuit usually takes place by
conductive adhesion. Before the integrated circuit is mounted onto
the bottom sheet or bottom plate, the integrated circuit forming
the control element is thinned on its underside, to fit into a chip
card, preferably to a thickness in the range of 0.1 mm to 0.2
mm.
The different improvements including a top sheet of plastic, a thin
bottom sheet, and a thinned-back integrated circuit allow a
thickness of the display unit of 0.55 mm in the region of the
integrated circuit and 0.45 mm in other regions of a
correspondingly constructed LCD display to be achieved.
In a particularly preferred embodiment of the present invention,
the bottom sheet may be made larger in one dimension than the front
region, that region of the bottom sheet that is larger than the
front region may be folded back on itself, and the integrated
circuit without a package may be connected to the folded-back
region of the bottom sheet. To one side, the bottom sheet is
consequently larger than it necessarily should be, to accommodate
the display element. The bottom sheet is consequently constructed
such that it can accommodate both the display elements and the
integrated circuit and is flexible enough to be folded back. The
folding back may take place directly onto the bottom sheet itself,
so that the rear side of the bottom sheet is in contact with
itself, but it may also be performed around a further supporting
layer, the bottom sheet then having to be led around the edge of
the supporting layer.
This configuration allows a particularly thin construction to be
produced in a simple way, since, for example, conductor tracks only
have to be provided on one side of the bottom sheet to allow the
display element(s) and the integrated circuit to be electrically
bonded simultaneously. A further advantage of this invention is
that one side of the bottom film may be specifically constructed
for the attachment of the components, while the other side has, for
example, adhesive properties.
In a further preferred embodiment of the invention, the display
element and the at least one control element are disposed on the
opposite surfaces of a substantially planar supporting structure.
Such a supporting structure is appropriate in particular whenever a
number of display elements not initially connected to one another
are to be used, or the rear side of the display element used is not
very suitable in respect of its surface structure for allowing a
connection to the at least one control element. The supporting
structure consequently represents a common base on which both the
display element and the control element can be optimally disposed.
In most cases, such a supporting structure will favorably be a
printed circuit board, preferably a flexible printed circuit board
that can serve at the same time for the electrical signal
transmission.
Electrical connection of the at least one display element and the
at least one control element by way of the electrical lines may be
performed in a variety of ways. For instance, the electrical lines
may be led directly through the supporting structure.
Alternatively or simultaneously, the electrical lines may also be
led around the edge of the supporting structure of the bottom plate
or bottom sheet.
The bottom sheet may preferably be made larger in one dimension
than the front region, that region of the bottom sheet that is
larger than the front region may be folded back on itself, and the
electrical lines may connect the front region of the bottom sheet
to the folded-back region of the bottom sheet. This configuration
is preferably combined with that described above, in which an
integrated circuit is applied directly to the folded-back region of
the bottom sheet.
If a surface suitable for the purpose, for example a folded-back
bottom sheet, is available, the electrical lines may be led out as
conductor tracks. This is appropriate in particular when a
folded-back bottom sheet is used.
The electrical lines may likewise be configured as a flexible flat
ribbon or as foil conductors, for example in the form of an inlay
sheet.
The various types of electrical lines that can be used according to
the invention can be combined with one another as desired,
according to the electrical or spatial requirements, to allow
optimum routing of the electrical lines to be achieved.
Specifically, when LCD display units are used, it is necessary to
lead the electrical lines around the bottom sheet or bottom plate,
since leading through the bottom plate, as is possible in the case
of conventional printed circuit boards, is not possible here.
In some applications, for example again in the case of chip cards,
it may cause thermal problems if heat is required when the
integrated circuit is mounted or if the heat-producing integrated
circuit is disposed directly behind the display elements, in
particular in the case of the typically sensitive LCD displays.
Therefore, in such cases, the integrated circuit is preferably
disposed at a distance from the actual display element(s). This can
be achieved by the control element being disposed in a region of
the rear region of which the front region has no display element
disposed on it. For example, it is possible to form on one side of
the display unit, for example in the bottom plate or bottom sheet,
an overhang, to the rear side of which the control element can be
attached.
In an alternative embodiment, the electrical lines may also be
direct connections between outputs of the at least one display
element and outputs of the at least one control element. In the
case of this particularly simple embodiment of the invention, the
outputs of the various elements involved, that is to say the
display elements and the control elements, are constructed in such
a way that, when their two undersides are placed one on top of the
other, they are directly opposed with their electrical outputs.
This allows the outputs to be directly connected by way of
electrical soldered joints. Consequently, in the case of this
embodiment, no continuing conductor tracks or other electrical
lines are necessary.
The display unit according to the invention may, furthermore, have
a signal line bus for the connection of the at least one control
element to a device that can or does display information on the
display unit. Such a signal line bus is only used, however, for the
transmission of the actual information signals, but not for the
transmission of direct control lines for activating the individual
segments of a display element. Consequently, considerably fewer
lines are required than in the prior art.
The invention is finally also directed at the use of a display unit
according to the invention for inclusion in compact devices, in
which the lateral dimensions in the direction of the plane of the
display are to correspond substantially to the size of the display
unit.
The use may be characterized in that the inclusion takes place in
chip cards. Suitable for performing inclusion is a cold adhering
technique with cyanoacrylate. Cold adhering techniques with
cyanoacrylate improves topography, does not subject the rear wall
of the card to thermomechanical stresses, and also cannot cause
thermally induced damage in the display unit.
The configuration according to the invention of the individual
elements of the display unit leads to devices that are much more
compact in plan view than was possible in the case of prior-art
devices.
Other features which are considered as characteristic for the
invention are set forth in the appended claims.
Although the invention is illustrated and described herein as
embodied in a display unit and a method for manufacturing a display
unit, it is nevertheless not intended to be limited to the details
shown, since various modifications and structural changes may be
made therein without departing from the spirit of the invention and
within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however,
together with additional objects and advantages thereof will be
best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic, sectional view showing a first embodiment
of a display unit with an LCD display, for example a matrix
display;
FIG. 2 is a sectional view showing a further preferred embodiment
of the display unit of the present invention, in which a number of
display elements, for example for figures and special symbols (i.e.
the "euro" symbol), are disposed on a supporting printed circuit
board;
FIG. 3 is a plan view showing a bottom sheet intended for folding
back;
FIG. 4 is a sectional view showing a further embodiment of the
display unit, which uses the bottom sheet shown in FIG. 3 that has
been folded; and
FIG. 5 is a sectional view showing a further embodiment of the
display unit with a control element that is attached directly to a
rear region of the top sheet that is not in contact with the liquid
crystal layer.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the figures of the drawings in detail and first,
particularly to FIG. 1 thereof, there is shown a sectional view of
a preferred embodiment of a display unit 1 of the present
invention. The display unit 1 may in this case be divided into a
front region 2 and a rear region 3. Here, the actual display
element 4 may be a commercially available LCD display, which
includes a top sheet 6, a liquid crystal layer 7, and a bottom
sheet 8. Attached to the rear side of the display element 4 is the
control element 5. In the present case, the control element 5 has a
package 5a. The package 5a protects activation electronics
contained in it against external influences or mechanical
damage.
On one side of the package 5a, a wiring interposer 9 leads out of
the package, is taken around the edge of the bottom sheet 8 and can
activate the liquid crystal cells of the liquid crystal layer 7
with its signal lines. The routing provided by the wiring
interposer 9 may take place by producing conductor tracks that lead
around the edge, but also by foil-conductor cables or flat ribbon
cables or by a bottom sheet with conductor tracks that is folded
back on itself. In the exemplary embodiment shown in FIG. 1, the
package 5a is kept at a distance from the bottom sheet 8 with the
aid of nubbins 10. However, it is also conceivable for the package
5a to be adhesively attached or fastened in some other way directly
onto the bottom sheet 8. Finally, it is also possible to dispense
with the package 5a and adhesively attach or in some other way
fasten the bare control electronics of the control element 5
directly onto the bottom sheet 8. The projecting edge of the bottom
sheet 8 around which the wiring interposer 9 is led is to be
thought of schematically, since smaller overhangs of the bottom
sheet 8 are also possible in the case of certain embodiments of the
invention and, on the other hand, the overhang might have to be
larger if there is lateral displacement of the integrated circuit
for thermal reasons. If available LCD displays are used, it must be
assumed that such an overhang of the bottom sheet is present, since
the flex circuit is usually provided there.
FIG. 2 shows a sectional view of a further exemplary embodiment of
the display unit of the present invention. Here, the individual
elements used are disposed on the two sides 12a, 12b of a printed
circuit board 12, which acts as a supporting structure. On the
front side 12a of the printed circuit board 12, four display
elements 4 are represented, in this case LED or LCD display modules
11, which are fastened to the printed circuit board 12 by their
display module legs 17. The fastening of the elements 4, or 11, may
also take place by adhesive or in some other way familiar to a
person skilled in the art, for example in order to free the
electrical connection via the display module legs 17 of mechanical
pressure.
It is possible to dispense with the printed circuit board 12, or
any supporting structure, if the individual display elements 4 are
directly connected to one another in such a way that they form a
unit.
Attached on the rear side 12b of the printed circuit board 12 is a
control element 5 in the form of a driver circuit 13, from which
there lead away IC legs 14, which serve for its electrical
connection to external elements.
The left-hand region of FIG. 2 shows an IC leg 14, a conductor
track 15, and a conductor leadthrough 16 through the printed
circuit board 12 forming an electrical signal connection between
the driver circuit 13 and the display module leg 17 of an LED or
LCD display module 11.
In the middle region of FIG. 2 it is shown how, again on the basis
of an IC leg 14, a conductor leadthrough 16 may be performed
directly through the printed circuit board 12, a conductor track 18
then leading on the front side 12a of the printed circuit board 12
to the display module leg 17, in order to achieve the electrical
connection between the driver circuit 13 and the display module
11.
FIG. 3 shows a bottom sheet 8 according to a particularly preferred
embodiment of the present invention, which is intended for use in
an LCD display element. Numerous conductor tracks 19, which serve
for supplying power to liquid crystal electrodes 20, have been
applied to the bottom sheet. These electrodes are usually made of a
material such as indium oxide or zinc oxide, in order to be
transparent and consequently not visible when the display unit is
viewed. The conductor tracks 19 are brought together in a circuit
contact region 21, in which the driver module or the control
element 5 can be adhesively embedded. A number of conductor tracks
22, which serve for the external connection of the control element
5 to a device, lead from the circuit contact region 21. When the
LCD display element is being assembled, the bottom sheet 8 is
folded along the folding line 23--23 and folded back on itself, so
that the control element 5 comes to lie on the rear side. The
folding at the folding line 23 has the effect that the control
element 5 comes to lie in a region of the bottom sheet 8 in which
there are no liquid crystals.
FIG. 4 shows a cross section through a display unit 1 according to
the invention that has been configured with the bottom sheet
according to FIG. 3. The control element 5, for example a
thinned-back integrated circuit, is disposed laterally from the
side of the actual display element 4. The folding-back of the
bottom sheet 8 results in the conductor tracks 19 being led around
the newly formed edge of the bottom sheet 8.
FIG. 5 shows a further embodiment of the display unit of the
present invention in cross section, with an LCD display being used.
In the case of this display, the bottom sheet 6 is made larger than
the liquid crystal layer 7. The control element 5 is not attached
to the bottom sheet 8, but directly to a rear region of the top
sheet 6 that is not in contact with the liquid crystal layer 7. The
electrical connection between the bottom sheet 8, bearing conductor
tracks 19, and the control element 5 takes place for example by a
further sheet 24, covered with conductor tracks, or in some other
suitable way. This embodiment has a particularly small thickness
and is therefore particularly suitable for use in chip cards.
The present invention allows display elements to be made in much
more compact dimensions than was previously possible. Embodiments
of the invention feature electrical lines that are shorter and
consequently freer from interference, and simplified signal
information transmission between the display unit and the
activating device. The overall construction of the unit remains in
the conventional area, so that use in existing devices should be
possible at any time. The routing of the wiring interposer over the
sheet edges means additional wiring area is no longer necessary.
The control element is located on the side that is more favorable
for leading away electric signals into a device. Moreover, the
control element is mechanically protected by the display elements
against intervention and damage. Finally, the control system
remains integrated in the display unit as a whole, so that the
latter can be marketed as a functional block that contains display
elements and control elements optimally made to match one
another.
The construction according to the invention makes it possible for
the first time to create LCD displays of a thickness that can be
accommodated in chip cards.
* * * * *